AES E-Library

A New Balanced Audio Input Circuit for Maximum Common-Mode Rejection in Real-World Environments

A new patented balanced input circuit emulates the extremely high common-mode input impedance which gives a quality audio transformer its hum and buzz rejecting advantage in real-world audio systems, where driving source impedances are rarely perfectly balanced. Compared to traditional active balanced circuits, the new circuit can produce CMRR improvements up to 80 dB but is only slightly more complex and requires no additional closely matched components.